IoTGateway/BSP/Android/Gettingstarted/How to use SD/MMC Card

SD/MMC card is supported in Android system. Starting in Android 6.0, Android supports adoptable storage, which is provided by physical media, like an SD card or USB, that is encrypted and formatted to behave like internal storage. 

Please refer to "Storage" section on the Android web site https://source.android.com/devices/storage/index.html

Android 6.0

fstab.device

/devices/soc0/soc/2100000.aips-bus/219c000.usdhc/mmc_host* auto auto defaults voldmanaged=sdcard:auto,encryptable=userdata

Check sysfs node

# cat /sys/block/mmcblk0/device/type
MMC
# cat /sys/block/mmcblk1/device/type
SD

SD Card is taken as an example:

Generate random file

# dd if=/dev/urandom of=data bs=1 count=1024

Back up

# dd if=/dev/mmcblk1 of=backup bs=1 count=1024 skip=4096

Write to SD

# dd if=data of=/dev/mmcblk1 bs=1 seek=4096

Read and Verify

# dd if=/dev/mmcblk1 of=data1 bs=1 count=1024 skip=4096
# diff data data1

If fail, it shows as below:

Binary files data1 and data differ

Restore

# dd if=backup of=/dev/mmcblk1 bs=1 seek=4096